1) Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus that eliminates unnecessary operations when papers are removed from a finisher prior to processing by the finisher.
2) Description of the Related Art
Some copiers, facsimile machines, printers, and the like are equipped with a finisher to perform post-printing processing, such as stapling and the like. Among these finishers, there are large-size finishers that perform post-printing processing of printed papers; for example, accumulating reams of printed papers in an internal intermediate tray unit until there are enough sheets for stapling, stapling the papers, and discharging the stapled papers to a main tray. There are also small-size finishers that leave a portion of a ream of paper at a processing position on the finisher, and then convey most of this portion to a tray outside the finisher where this portion is stapled and discharged.
Since, in the large-size finisher, the reams of stapled paper are discharged to the main tray from the edge opposite the stapled edge, it is easy for the edges of the reams of paper to become separated and cause a discharge jam. Japanese Patent Application Laid-Open No. 2000-191224 discloses a method to avoid a jamming of stapled reams of paper during discharge.
On the other hand, in the small-size finisher a portion of the ream of paper remains in the finisher, and then most of this remaining portion is conveyed to a tray outside the finisher for stapling and discharge; so few paper jams occur on the conveyance route. Since papers are discharged outside the finisher prior to stapling, there are many users who, in a hurry, mistakenly assume that stapled papers are being discharged, and accidentally remove the papers before stapling.
Conventional image forming apparatuses employ a processing procedure wherein the removal, prior to stapling, of papers discharged outside the finisher is judged to be an abnormal termination of a normal image forming operation; and the conventional image forming apparatus is configured to repeat the image forming operation.